Asphalt-based roofing materials, such as roofing shingles, roll roofing, and commercial roofing, have long been installed on the roofs of buildings to provide protection from the elements and to give the roof an aesthetically pleasing look. Typically, asphalt-based roofing material is constructed of a substrate such as a glass fiber mat or an organic felt mat, an asphalt coating on the substrate to provide a water barrier, and a surface layer of granules embedded in the asphalt coating. The granules protect the asphalt from deterioration due to exposure to UV and IR radiation from the sun and direct exposure to the elements.
A common method of manufacturing asphalt-based shingles is to advance a sheet or web of the substrate material through a coater, which coats the web with liquid asphalt forming a hot tacky asphalt coated strip. The asphalt coated strip is typically then passed beneath one or more granule dispensers, which discharge or dispense protective and decorative surface granules onto at least selected portions of the moving asphalt coated strip. A granule dispenser may be as simple as a direct feed nozzle fed by an open hopper that is filled with granules or as complex as a granule blender. The result is a strip of shingle stock at, least partially covered with granules, which can later be cut to size to form individual shingles, cut and rolled to form a rolled shingle, or otherwise processed into final products.
In some shingle manufacturing processes, there is a need to deliver granules at intermittently timed intervals such that granules are deposited on the asphalt coated strip in spaced patterns. In such cases, several mechanisms have been used in the past to start and stop the delivery of granules in a controlled manner. For example, a fluted roll has been inserted at the bottom of a granule dispenser nozzle such that rotation of the fluted roll pulls a charge of granules from a granule hopper and throws or drops the granules a set distance (generally over 12 inches) onto the asphalt coated strip below. In some cases, the charge of granules slides down a polished curved surface toward the substrate material. The curved surface in conjunction with gravity accelerates the charge of granules to approximately the speed of the moving asphalt coated strip below and deposits the charge of granules gently onto the asphalt.
Prior systems and methods of depositing granules onto an asphalt coated strip in shingle manufacturing have exhibited a variety of inherent problems. Chief among these is that as the speed of production increases, meaning that the speed of the moving asphalt coated strip increases, the edges and patterns of dispensed charges of granules on the asphalt become less and less defined. Eventually, the deposited patterns of granules are so indistinct and distorted as to be unacceptable in appearance, coverage, and protection. Trailing edges in particular of a deposited charge of granules become more and more smeared out as the speed of production is increased and dispensed charges of granules exhibit unacceptable trailing patterns. As a result, granule delivery systems and methods in the past have been practically limited to production speeds below about 800 feet per minute (FPM) of asphalt coated strip travel, even though other areas of production are capable of moving much faster.
There is a need for a granule delivery system and method for use in shingle manufacturing that is capable of delivering a charge of granules at intermittently timed intervals onto a moving asphalt coated strip with precision, definition, and controllability at manufacturing speeds of over 800 FPM and even over 1000 FPM. It is to the provision of such an apparatus and method that he present invention is primarily directed.